We are creating a GEF editor where we need to have some parts scrolling in only one direction.
I'm looking for help/hints on how to accomplish this.

See the attached image for the intended layout.

The main area of the editor is to be scrolling normally, i.e. both vertically and horizontally.
At the top and the bottom we will have parts which only scrolls horizontally.
On the left hand side, there will be a part which only scrolls vertically.
And as shown in the image, there will be 2 "dead zones" which doesn't scroll at all.

The vertical scroll for the left hand part shall be the same as for the main area, i.e. when the main area is scrolled vertically the area on the left side is scrolled the same vertical amount.

And the same applies to the horizontal scroll for the top and bottom parts.

With a little help I found that the GEF Rulers does pretty much what we need.
So I'm going to dig into how they are implemented and try to reuse that approach.
The Rulers can be tried out in the GEF Logic example, just make them visible using the View > Rulers action when running the example.